The present invention relates to a pellet for a radioactive seed used for medical treatments.
Discrete brachytherapy sources have been known to provide an effective method in the medical treatment of diseased tissues. These discrete sources are implanted into a patient at the site of the diseased tissue. To effectively treat the patient, it is desirable to have such a source which will irradiate the diseased tissue while minimizing damage to nearby healthy tissue. Therefore, it is desirable to have a source which will uniformly irradiate an area being treated with a controlled desired dosage of irradiation. Also desirable is a method of accurately detecting the location of the sources after implantation. The usual construction of such sources comprises a radioactive source which is radiopaque by itself or has an X-ray detectable marker disposed therein.
Radioactive iodine sources used in radiation therapy are known and described, for example, in Lawrence U.S. Pat. 3,351,049 and Kubiatowicz U.S. Pat. 4,323,055. The radioactive iodine sources described in those patents generally comprise a container for a carrier body of radioactive material and an X-ray marker. The container is generally made from titanium or stainless steel, thereby providing good mechanical strength of the container with minimum absorption of radiation. An X-ray marker is disposed within the container to permit identification by X-ray photographic techniques of the position and number of seeds.
The carrier body disclosed in the Lawrence patent is constructed of a material such as nylon which will chemically or physically capture the selected radioisotope utilized as a source for radiation and maintain a uniform distribution of the isotope in a fixed bed. A marker material is also disposed within the container for X-ray detection. The patent to Kubiatowicz discloses an X-ray carrier body preferably comprising a silver or silver coated rod. Silver is used because it provides good X-ray detection and because radioactive iodine can be easily attached to the surface thereof by chemical or electroplating processes. However, the interaction of the X-rays from I-125 with the silver produces still lower energy radiations characteristic of silver thus degrading the total I-125 spectrum from the source.
However, it will be appreciated that the prior art fails to recognize a convenient and advantageous method for providing a radioactive iodine source which provides maximum radioactive absorption while being X-ray detectable along its longitudinal axis, and without distorting the characteristic X-ray spectrum of I-125. Also, the prior art fails to recognize a method for easily manufacturing quantities of radioactive sources having a desired controlled radioactivity.